This invention relates to deicers and more particularly to pneumatic deicers for helicopter blades employing an elongated boot of a resilient material which is inflatable to remove ice formation on the rotating propeller blades.
Protective apparatus for preventing the accumulation of ice on a surface such as fixed aircraft wings and struts have employed electrical as well as pneumatic deicers. With respect to helicopter rotating blades, only electrical deicers have been used heretofore to maintain a low aerodynamic drag. The present invention provides a unique combination of a thin composite material forming a pneumatic deicer boot or deicer pad with spanwise and chordwise passageways providing improved dynamic properties for use on a helicopter rotating blade providing excellent ice removal characteristics.
Electrical deicers were used exclusively on helicopter blades because of the need to control the rotating mass accurately, maintain aerodynamic balance, precision contour thereof, and proper aerodynamic balance at high operating velocities. In helicopter rotary airfoils, the bending and centrifugal stresses are much different and more complicated than in either fixed wing airfoils or airplane propellers due to the design characteristics of the airfoil. Cyclic pitch control is also encountered in the rotary airfoil of a helicopter blade since the rotary airfoil moves first into the wind and then with the wind. Thus the helicopter blade design requires a complex airfoil design requiring the consideration of many factors and therefore only electrical deicers were used on helicopter blades to minimize design change factors. The present invention however is directed to the use of a unique combination of pneumatic design characteristics into a deicer pad which are able to provide a low aerodynamic drag and thereby overcomes prior objections to its use in a rotary airfoil. Such design also provides a deicer pad that has the unique ability to effectively remove ice formations at relatively low cost, low weight and at low operating power.